You cannot safely sleep 8 hours of real sleep in 4 hours
Use a consistent sleep schedule every day
Go to bed and wake up at the same time
Get bright light in the morning
Avoid caffeine 6 to 8 hours before bed
Avoid alcohol before sleep
Avoid nicotine before sleep
Keep your bedroom dark, quiet, and cool
Stop screens 1 hour before bed
Use a short wind-down routine
Exercise regularly, but not right before bed
Avoid heavy meals late at night
Limit long naps during the day
If you must sleep less, use a short nap only as a supplement
Try a 20 to 30 minute power nap
Try a 90 minute full sleep cycle nap
Prioritize sleep quality over trying to cut sleep time
If you are always sleepy, get checked for sleep problems
If you have insomnia, seek medical help
If you snore loudly or stop breathing in sleep, seek medical help